Inorganic liquids could be used to improve the performance of fuel cells, say researchers in the US.

Austen Angell and colleagues from Arizona State University have used inorganic ammonium salts as electrolytes in fuel cells that operate in the temperature range from 100-200ºC. The performance of their cells is comparable to the commonly used phosphonic acid fuel cell, even before the performance of the electrolyte has been optimised.

Until now, fuel cells have commonly used large organic cations, but simple mixtures of inorganic salts are also liquid at low temperatures, and are highly conducting. Angell said that the organic cation is not necessary for the electrolyte to function effectively. He went on to say 'For the purposes of high current density cells, the removal of the organic component seems to bestow an advantage.'

An additional benefit of using these electrolytes in fuel cells is that they can be neutral and non-corrosive, while still highly conducting and effective as proton carriers, said Angell. 'Their benign character not only simplifies cell construction but also opens the door to many alternative catalysts, including heat stable enzymes.'

George Chen, associate professor in electrochemical technologies at the University of Nottingham, UK, said that the work 'opens a new economical route towards a wide choice of electrolytes for fuel cell development'. He continued: 'These electrolytes may enable the use of new and more affordable materials for other elements in fuel cells, such as non-precious metal catalysts that would not work in a conventional aqueous environment, but may perform ideally in these simple and cheap salt mixtures.'

Ruth Needham